Protection of molten baths



Fatented Aug. 14, 1934 warren stares PATENT orrica Hutchinson,

Pittsburgh, Pa.,

assignors to Pennsylvania Salt Manufacturing Company, Pittsburgh, Pa", acorporation oi Pennsylvania No Drawing. Application March l, 1932,

Serial No. 596,148

13 Claims.

This invention relates generally to a method of protecting molten bathsfrom oxidation and also conserving the heat of the bath by covering thesurface of the bath with a material con- 5 taining aluminum oxide as itspredominant constituent.

Although the invention is useful in protecting metal baths in general,whether the baths are used as galvanizing baths, baths for tempering orheat treatment of articles in general, or for other purposes, it isparticularly useful in protecting a spelter bath used in galvanizingfrom oxidation and also conserving the heat of the oath.

Galvanizing baths of spelter are now either left entirely unprotected orin some cases are covered with a material which provides insufficientprotection from oxidation and also allows the loss of a large proportionof heat which may be and it also acts as a heat conserving cover,

thereby reducing the fuel cost. The decreased oxidation of a bathprotected by such a covernecessary to remove the oxides formed. Thealuminum oxide is preferably added to the bathv in granular or powderedform, the amount being dependent upon the surface area of the bath andthe temperature of the bath. The oxide of aluminum is substantiallyiniusible at the temperature of the galvanizing. bath and, therefore,acts as a better heat insulation than is the case where more easilyfusible materials are used.

The invention contemplates not only adding oxide of aluminum to thebath, but extends to the use of materials which will be converted at thetemperature of the bath into oxide of aluminum. Thus, hydrate of aluminaor other suitable material may be employed. The hydrate of alumina isconverted by contact with the molten-metal either partially or whollyintooxide of aluminum which has high heat insulating and oxidationresisting properties. In the converconserved by providing a cover ofmaterial in acing reduces the skimming which is ordinarily sion of thehydrate of alumina into the om'de of (C1. it-76.2)

aluminum, it passes through the stage of monohydrate of alumina whichhas very high heat insulating propertiesf The extent of the conversionwill depend upon the particular temperature used, in some cases theconversion be- 69 ing complete while in others the covering layer If amaterial is used which contains aluminum not in the form of oxide ofaluminum, but which is converted after addition to the bath into oxideof aluminum, tlieadded material should contain 75 -a sumcient amount ofaluminum so that after it is converted into oxide of aluminum, the oxideof aluminum will constitute the predominant constituent of the coveringlayer.

We have found from experiments that when a galvanizing bath is protectedby a covering of aluminum oxide, a saving of 58% of the fuel may beeffected. The saving in fuel is an additional advantage over the savingin 'spelter because of the reduced oxidation of the bath due to thecovering layer.

The covering may be put on the top of molten metal in an ingot mold forthe purpose of keeping the top hot until the rest of the ingot hassolidified.

Although the invention has been describedparticularly in connection witha spelter bath. used for galvanizing, the protective covering containingaluminum oxide as its predominant constituent may be used for protectingother metallic baths, and the invention may be otherwise embodied orpracticed within the scope of the :iol-x lowing claims.

We claim:

1. The method of insulating and protecting molten baths from oxidation,which comprises adding to the bath a material which contains freealuminum oxide as its predominant constituent. z

2. The method of insulating and protecting 105 molten metallic bathsfrom oxidation, which comprises adding to the bath a material whichcontains free aluminum oxide as its predominant constituent.

3. The method of insulatingand protecting 110 molten baths fromoxidation, which comprises adding aluminum oxide to the bath.

4. The method of insulating and protecting molten metallic baths fromoxidation, which comprises adding to the bath a covering of materialcontaining free aluminum oxide as its predominant constituent and whichis substantially infusible at the temperature of the bath.

5. In the method of coating articles by dipping them in a molten bath,the step comprising adding to the bath a material which contains freealuminum oxide as its predominant constituent.

6. In the method of coating articles by dipping them in a molten bath,the step comprising adding to the bath a material which contains freealuminum oxide as its predominant constituent, and which issubstantially iniusible at the temperature of the bath.

7. In the method of galvanizing wherein a molten bath of spelter isused, the step comprising covering the surface of the bath with amaterial which contains free aluminum oxide as its predominantconstituent.

8. In the method of galvanizing wherein a molten bath of spelter isused, the step comprising covering the surface of the bath with amaterial which contains free aluminum oxide as its predominantconstituent and which is substantially infusible at the galvanizingtemperature of the bath.

9. The method of insulating and protecting molten baths oi. metal fromoxidation, which comprises adding to the bath a material which containshydrate of alumina, and converting the hydrate of alumina into oxide ofaluminum, the material added to'the bath containing hydrate of aluminain such amount that the oxide of aluminum formed therefrom constitutesthe predominant constituent.

10. The method of insulating and protecting molten baths of metal fromoxidation which comprises adding to the bath a material containinghydrate of alumina as its predominant constituent, and converting thehydrate of alumina into the monohydrate of alumina.

11. The method of insulating and protecting molten baths from oxidation,which comprises adding to the bath a material consisting substantiallyentirely of aluminum oxide.

12. In the method of galvanizing wherein a molten bath. of spelter isused, the step comprising covering the molten bath with a materialconsisting substantially entirely of aluminum oxide.

13,. The method of insulating and decreasing oxidation of baths whichare free from substantial amounts of aluminum, which comprises coveringthe bath with a material which contains free aluminum oxide at itspredominant constituent.

JAR ES S. GUMMERT. JOHN E. HUTCHINSON.

